Kronan
Regent
As I understand it, on a phone you can buy with gold on the image of the hand, not just on the button.
All I can say is: WOW, you are correct. Another opportunity lost for years..... IN 6 YEARS of PLAYING, I have NEVER EVER seen that feature and no one I know of has mention it either, or KNEW it existed!!! Why do we have to find these kinds of deep dark game secrets like this? Where is it documented? My bet is that someone found that by accident. 99.99% of people playing see a button and press it to affect their desired result.
Regardless of this new "ENLIGHTENMENT", the proper way to design this is to have the buttons placed as in @Tanmay11 post: https://forum.beta.forgeofempires.com/index.php?threads/buying-fps.15379/post-131464